An NCI Working Group on Epidemiology Data Resources was established more than 10 years ago with Dr. Beebe as chairman. Its charge is to develop new data resources and improve existing resources of value for cancer epidemiology. Targeted issues have included the use of Social Security files for the ascertainment of mortality, the development of a database for occupational mortality based on (1) death certificates and (2) the Current Population Survey, the effective use of the hospital discharge database of the Department of Veterans' Affairs, management of the National Death Index, facilitation of record linkage by computer, access to the administrative files of Federal agencies, and access to the taxpayer address file of the Internal Revenue Service. In addition the Working Group reviews for Dr. Fraumeni all Master Order Agreement-Requests for Proposals developed in the Epidemiology and Biostatistics Program. A new activity involves an exploration of the potential value of a file of about 40,000 sera collected from Air Force recruits in the Korean War era.